Irving Kahn was born in Manhattan on Dec. 19, 1905 (the stock market rebounded that day), to Mamie Friedman and Saul Kahn. His father sold light fixtures. Irving graduated from DeWitt Clinton High School in the Bronx and enrolled in City College, but quit after two years to become a clerk at Kuhn, Loeb & Company. He immediately made a beeline for Ben Graham, a trader at the Cotton Exchange with a reputation for outperforming the market. Mr. Graham recruited Mr. Kahn to be a part-time teaching assistant at Columbia Business School, where Mr. Graham taught after trading hours. His acolytes included Warren Buffett. Both Mr. Kahn and Mr. Buffett were so taken with him that they bestowed the middle name Graham on their sons. At Columbia, Mr. Kahn also met Ruth Perl, who was studying for her doctorate in psychology. They married in 1931. She died in 1996. Beside his sons Thomas and Alan, he is survived by seven grandchildren and eight great-grandchildren. A disciple and later partner of Benjamin Graham, the contrarian advocate of “value investing,” Mr. Kahn would go on to work at Abraham & Company and Lehman Brothers, which he left in 1978 to open Kahn Brothers Group with two of his sons, Alan and Thomas. When he died, he was chairman of Kahn Brothers, a privately owned investment advisory and brokerage firm, which manages $1 billion through its subsidiaries. He was also the last surviving member of what had been described as the oldest living sibling quartet. One sister, Lee, died in 2005 at the age of 101. Another sister, Helen Reichert, was seven weeks shy of her 110th birthday when she died in 2011. Their younger brother, Peter Keane, died last year after turning 103.